Two-stroke engines of conventional construction usually include a so-called crank-chamber scavenging, whereby the sucked-in fuel-air mixture is led first of all into the crank chamber, which receives the crankshaft and is surrounded by the crankcase. There, the fuel-air mixture is supercharged by the piston sliding downwards in the cylinder in the working stroke, and is then transferred, when the piston frees an associated transfer passage in the cylinder wall, to the combustion chamber. In the next stroke, the piston slides upwards and compresses the transferred mixture in the combustion chamber, while at the same time a fresh mixture is sucked into the crank chamber. The terms “up” and “down” refer to an upright cylinder arrangement with the cylinder head located on top.
In a two-stroke spark-ignition engine, ignition of the fuel-air mixture compressed by the piston is effected in the combustion chamber through an active ignition device in the form of a spark plug with associated voltage supply and release electronics, when the piston passes the dead center. The burnt mixture or exhaust gas is released from the combustion chamber at the end of the working stroke through an outlet passage then freed by the piston and is, as a rule, led through an exhaust manifold into the exhaust or muffler section.
Two-stroke engines can be configured for an internal mixture generation with direct injection of the liquid fuel into the combustion chamber or for an external mixture generation in a carburettor. In the carburettor, the liquid fuel is injected into the air flow, which is sucked in or pressed in through a charging device, and atomized. A crank-chamber scavenging is in most cases combined with an external mixture generation.
Usually, a gasoline-oil mixture is supplied as fuel to such two-stroke engines, the addition of oil serving for lubricating the motor. Especially in recent times, it is desired, due to corresponding financial incentives, to replace (regular) gasoline by kerosene, which is normally used as fuel for gas-turbine engines, or also by diesel fuel.
Corresponding attempts to upgrade a two-stroke spark-ignition engine for an operation with diesel or kerosene, are known, for example, from U.S. Pat. No. 5,855,192. For an improved ignition behavior, in particular in the stage of the motor start, a heating of the cylinder head with the help of a glow pencil applied there, which is independent of the spark plug, is provided there. The cylinder head is in this case subjected to a relatively high thermal stress, which generally requires the use of correspondingly high-quality and high-temperature resistant materials and of, for example, ceramic components in the cylinder. Nevertheless, on the whole, the running behavior of motors modified in this manner zierter is not convincing.